We developed in vitro pharmacodynamic models to evaluate the activity of antibiotics against biofilms made of S. aureus, S. pneumoniae or P. aeruginosa. We showed that antibiotic efficacy and relative potency are considerably reduced in biofilms as compared to planktonic cultures. With S. aureus, we found that biofilms made of clinical strains isolated from patients suffering from persistent infections are still more refractory to antibiotics. We could demonstrate that this was mainly due to a default of penetration of the antibiotics within these biofilms, which could attribute to the matrix composition (polysaccharide content). On these bases, we are exploring innovative strategies in order to disrupt this matrix and increase antibiotic activity.
In parallel, we have also started to develop more pertinent models of biofilms, like biofilms growing in artificial sputum medium mimicking the viscoelastic properties of the mucus found in the respiratory tract of patients suffering from cystic fibrosis, or multispecies biofilms developing on orthopedic implants.